[Animal experiment studies on the mechanism of action of flunitrazepam (Rohypnol) on the circulation and respiration]

In 29 experiments performed on relaxed cats with artificial respiration, the effects of 0.015; 0.03; 0.06 mg flunitrazepam per kg body weight i.v. with N2O basal anaesthesia and of 0.06 mg flunitrazepam per kg without basal anaesthesia were examined in respect to mean arterial blood pressure, heart rate and the efferent action potentials of the N. sympathicus and the N. phrenicus. In all experiments, a mild and short-term reduction in blood pressure, a slight tachycardia and a very brief inhibition of the sympathetic nerve were observed. Definite actions exercised by flunitrazepam consisted of an inhibition of the respiratory centre which was due to a reduction of the extent and intensity of the inspiratory discharges of the phrenic nerve, although the breathing rate was increased. A comparison of the tests with flunitrazepam alone and in combination with N2O yielded definite differences only in the case of the asphyxia tests. The combination produced a significant inhibition of the vagus centre which was absent when flunitrazepam was used alone.